The overall objective of this study is to test the efficacy of an evidence-based, enhanced prescription drug (Rx) container label design to improve older patients'understanding of instructions for use. More than one third of the 1.5 million adverse drug events that occur in the United States each year happen in outpatient settings. Problems with Rx labeling were specifically cited as a leading root cause, as patients may unintentionally misuse a prescribed medicine due to improper understanding of instructions. The elderly are at greatest risk;they take more drugs, are more likely to have limited health literacy, and visual/cognitive impairments may further limit comprehension. Instructions on the Rx container itself are especially critical as the most tangible information source repeatedly used by patients. Studies have also shown that supplementary Rx materials and sources are insufficient or not used by patients. Yet problems are well documented with Rx container labels. Only minimal standards and regulations exist regarding their content and format, thus the quality of Rx label instructions vary greatly by pharmacy and prescribing physician. This study will advance the science related to Rx labeling practices. Specific aims are to: 1) refine and pilot test an existing enhanced Rx container label prototype among older adults, 2a) evaluate the efficacy of the enhanced Rx container label to improve patient understanding of dosage/usage instructions and medication risks compared to the current standard label design, and 2b) evaluate the efficacy of the enhanced Rx container label to improve older diabetic patients'understanding and actual use of their own medicine. Research will be conducted in three phases: 1) Preparation, 2) Comprehension Testing, and 3) Actual Use Assessment. An existing evidence-based label prototype will be refined and piloted among older adults at three primary care settings. In Phase 2, patients'ability to comprehend instructions on `enhanced'labels will be compared against two current standard labels issued from leading pharmacy chains. In the final phase, we will take advantage of a rare opportunity within a pharmacy practice to test the efficacy of an enhanced Rx label design in the context of actual use. This is unique, as software and labeling systems currently used by U.S. pharmacies limit the ability to change Rx label format and content. A randomized trial will be conducted among 960 diabetic patients receiving care at 11 safety-net clinics;all of whom receive their Rx regimens through one central-fill pharmacy. Correct understanding and self-reported adherence (3-month follow-up) will be compared between the enhanced Rx label and the current standard label in use. Exploratory analyses will use pharmacy and medical records data at 1 year. The proposed study seeks to remedy a well-recognized and serious national problem of poorly communicated Rx instructions by targeting the most tangible and frequently-used informational source: the container label. Given the unacceptably high prevalence of medication error and the greater risk incurred by the elderly who face health literacy barriers and more complex Rx regimens, strategies must be sought now to inform standards for health care providers (pharmacists and physicians) on how to deliver clear and simple Rx information. This study will advance the science related to Rx labeling practices. Findings will directly inform clinical practice and state and federal policies for improving patient medication information and safety.